<html>
    <head>
        <title>Test</title>
        <style>

progress.custom {
  appearance:none;  
  background-color:gold;
  color:red;
}

        </style>
        <script></script>
    </head>
    <body>

      <p>default styling: <progress value="0.5" /></p>
      <p>custom styling: <progress.custom value="0.5" /></p>

    </body>
</html>